1. Field of the Invention
The present invention relates to a heat transfer element disposed in a casing of an electronic device to transfer heat generated by a heating element in the electronic device, and to a cooling device and an electronic device having the heat transfer element.
2. Description of the Related Art
An electronic device, for example, a so-called notebook personal computer, includes a display section and a main body. The main body has a keyboard, and a heating element, such as a CPU (Central Processing Unit), disposed therein. The heating element generates heat during operation. In order to radiate heat of the heating element out of a casing of the main body, a cooling device is disposed in the casing.
This type of cooling device has a heat pipe. The heat pipe is also called a heat transfer element, and includes a metal container filled with condensable working fluid. Heat from the heating element is transmitted to a heat input section of the container, and the working fluid is thereby evaporated into vapor adjacent to the inner wall of the heat input section. The working fluid then moves to a heat output section of the container where the pressure and temperature are low, condenses adjacent to the inner wall of the heat output section, and emits latent heat of condensation.
In this way, heat from the heating element is radiated to, for example, a radiating fin in the heat output section by the heat pipe (for example, see Japanese Unexamined Patent Application Publication No. 2001-237579, page 5 and FIG. 9).
Containers of heat pipes are conventionally made of metal in order to increase-the thermal conductivity, as described above. With weight reduction of electronic devices, there is a demand to reduce the weight of the heat pipes. It is, however, difficult to further reduce the weight of the heat pipes made of metal.
Metal containers have a sealed structure in which they are hermetically sealed with their ends covered with caps to ensure a vacuum therein. Therefore, the containers are expensive and lack reliability because, for example, working fluid is apt to leak during actual use.